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  Subjects -> ENGINEERING (Total: 2272 journals)
    - CHEMICAL ENGINEERING (190 journals)
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    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1204 journals)
    - ENGINEERING MECHANICS AND MATERIALS (381 journals)
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CHEMICAL ENGINEERING (190 journals)                     

Showing 1 - 190 of 190 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 7)
ACS Sustainable Chemistry & Engineering     Hybrid Journal   (Followers: 5)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 5)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 8)
Advanced Chemical Engineering Research     Open Access   (Followers: 32)
Advanced Powder Technology     Hybrid Journal   (Followers: 17)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 5)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27)
Advances in Chemical Engineering and Science     Open Access   (Followers: 56)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 11)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 10)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 8)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 14)
Biofuel Research Journal     Open Access   (Followers: 4)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Catalysts     Open Access   (Followers: 8)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
Chemical and Engineering News     Free   (Followers: 14)
Chemical and Materials Engineering     Open Access   (Followers: 13)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 13)
Chemical and Process Engineering     Open Access   (Followers: 28)
Chemical and Process Engineering Research     Open Access   (Followers: 24)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 32)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 17)
Chemical Engineering and Science     Open Access   (Followers: 19)
Chemical Engineering Communications     Hybrid Journal   (Followers: 14)
Chemical Engineering Education     Full-text available via subscription  
Chemical Engineering Journal     Hybrid Journal   (Followers: 46)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 24)
Chemical Engineering Research Bulletin     Open Access   (Followers: 12)
Chemical Engineering Science     Hybrid Journal   (Followers: 28)
Chemical Geology     Hybrid Journal   (Followers: 20)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 4)
Chemical Reviews     Full-text available via subscription   (Followers: 181)
Chemical Society Reviews     Full-text available via subscription   (Followers: 42)
Chemical Technology     Open Access   (Followers: 16)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry of Materials     Full-text available via subscription   (Followers: 255)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 4)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 21)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 37)
Corrosion Reviews     Hybrid Journal   (Followers: 6)
Crystal Research and Technology     Hybrid Journal   (Followers: 6)
Current Opinion in Chemical Engineering     Open Access   (Followers: 7)
Designed Monomers and Polymers     Open Access   (Followers: 2)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Eksergi     Open Access  
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 6)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 2)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 6)
Heat Exchangers     Open Access   (Followers: 3)
High Performance Polymers     Hybrid Journal   (Followers: 1)
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 10)
Indonesian Journal of Chemical Science     Open Access   (Followers: 1)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 12)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 23)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access   (Followers: 1)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 6)
International Journal of Waste Resources     Open Access   (Followers: 4)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 5)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 6)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 14)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 137)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 12)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 7)
Journal of Chemical Engineering     Open Access   (Followers: 20)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 5)
Journal of Chemical Sciences     Partially Free   (Followers: 22)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 15)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Combinatorial Chemistry     Full-text available via subscription   (Followers: 1)
Journal of Crystallization Process and Technology     Open Access   (Followers: 8)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 7)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access   (Followers: 1)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal   (Followers: 1)
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 9)
Journal of Materials Science and Chemical Engineering     Open Access  
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 6)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 8)
Journal of Organic Semiconductors     Open Access   (Followers: 5)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 6)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 9)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 6)
Journal of Polymers     Open Access   (Followers: 6)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 2)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 314)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 2)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 9)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access   (Followers: 5)
Jurnal Reaktor     Open Access  
Jurnal Rekayasa Kimia & Lingkungan     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Konversi     Open Access  
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 2)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 16)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Modern Chemistry & Applications     Open Access  
Molecular Imprinting     Open Access  
Nanochemistry Research     Open Access  
Nanocontainers     Open Access   (Followers: 1)
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 4)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 4)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 3)
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 127)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 16)
Polyolefins Journal     Open Access  
Powder Metallurgy Progress     Unknown   (Followers: 1)
Powder Technology     Hybrid Journal   (Followers: 13)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 6)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 4)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 4)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 2)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

           

Journal Cover Chemical Engineering Science
  [SJR: 1.073]   [H-I: 135]   [28 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [3051 journals]
  • Evaluation of contact force models for discrete modelling of ellipsoidal
           particles
    • Abstract: Publication date: 23 February 2018
      Source:Chemical Engineering Science, Volume 177
      Author(s): Kamyar Kildashti, Kejun Dong, Bijan Samali, Qijun Zheng, Aibing Yu
      Discrete element method (DEM) has been widely used to study granular materials. However, how to model non-spherical particles is still challenging. Ellipsoidal particles are a typical kind of non-spherical particles in DEM simulations. There are three common methods to calculate the overlap and contact force between two ellipsoidal particles, namely, geometric potential (GP), common normal (CN) and overlap region (OR) methods. These methods are based on different physical concepts and hence will give different results. However, the comprehensive evaluation of these methods is still lacking, leaving DEM users no solid reference for selecting algorithms. In this paper, we conduct detailed comparisons on the penetration depth, contact plane and contact point predicted by the three methods. Particularly, using the orientation discretization method, the results are compared in all orientations quantitatively. It is shown that the difference between GP and CN is the largest whereas OR is always in between. The difference in contact point is relatively small when overlap ratio is small, whereas the difference in contact plane can always be large. Further, the results are directly compared to those obtained from sub-particle scale finite element analyses, which reveals that CN can always accurately predict contact plane and most times contact point, while GP are relatively better in predicting force magnitude. This study not only gives a more clear and comprehensive evaluation of different contact force models for ellipsoidal particles but also establishes an effective framework for comparing and verifying contact force models for general non-spherical particles.
      Graphical abstract image

      PubDate: 2017-11-15T18:06:36Z
       
  • Oxygen permeation properties of novel BaCo0.85Bi0.05Zr0.1O3−δ
           hollow fibre membrane
    • Abstract: Publication date: 23 February 2018
      Source:Chemical Engineering Science, Volume 177
      Author(s): Zhenghui Qiu, Yadi Hu, Xiaoyao Tan, Siti Salwa Hashim, Jaka Sunarso, Shaomin Liu
      In this work, we characterized and tested the oxygen permeation properties of BaCo0.85Bi0.05Zr0.1O3−δ (BCBZ) hollow fibre membranes fabricated by a combined phase inversion for spinning and sintering route using polyetherimide (PEI) as the polymer binder. The powder X-ray diffraction results showed that the BCBZ powder for spinning had to be calcined at around 950 °C to form a hexagonal phase structure, while the hollow fibre precursors were sintered at 1150–1200 °C to form the cubic perovskite structure for oxygen permeation. It displayed the highest oxygen flux of 7.3 cm3 (STP) cm−2 min−1at 950 °C under an air/He gradient. The theoretical correlation of the oxygen fluxes at different operating conditions showed that the oxygen permeation through BCBZ fibre was limited by surface exchange reactions. Carbon dioxide (CO2) resistance of BCBZ hollow fibre was tested by exposing it to alternating different sweep gas containing helium (He), 20% CO2 in He, 80% CO2 in He, and pure He. Despite the significant reduction in oxygen fluxes upon subjected to CO2-containing sweep gases due to the strong CO2 sorption on the membrane surface, no permanent damage on the membrane was detected and the original flux could be recovered at the end of the 105-h test once the sweep gas was switched back to helium. This result clearly highlights the high CO2 resistance of BCBZ hollow fibre membrane due to the presence of Zr4+ with higher acidity than Co2+ in BCBZ perovskite lattice. High CO2 tolerance enables the membrane use as membrane reactors for more advanced applications where the presence of CO2-containing atmosphere is unavoidable.

      PubDate: 2017-11-15T18:06:36Z
       
  • Experimental investigation of mass transfer performance in laboratory- and
           pilot-scale structured-packing columns under roll motion
    • Abstract: Publication date: 23 February 2018
      Source:Chemical Engineering Science, Volume 177
      Author(s): Xiao-ning Di, Shu-jie Chen, Wen-hua Wang, Yi Huang
      Influence of roll motion on the mass transfer performance in laboratory- and pilot-scale structured-packing columns was investigated. A six-degree-of-freedom motion parallel platform was adopted to mimic different sea states of roll motion, and the relative change in the mass-transfer area caused by roll motion was obtained using an air-NaOH system. The experimental results showed that both enhanced and deteriorative mass transfer phenomena could be induced by roll motion, which results from the combined effect involving the operating conditions, packing types and sea states. Based on these results, a nominal maximum rolling velocity was proposed. The nominal maximum rolling velocity was positively correlated with the relative change in the mass-transfer area. Furthermore, the results indicated that tilt could be regarded as an extreme sea state of roll motion.

      PubDate: 2017-11-15T18:06:36Z
       
  • Kinetic modeling of CO2 adsorption on an amine-functionalized solid
           sorbent
    • Abstract: Publication date: 23 February 2018
      Source:Chemical Engineering Science, Volume 177
      Author(s): Wonho Jung, Junhyung Park, Kwang Soon Lee
      A kinetic model of CO2 adsorption on an amine-functionalized silica sorbent, 0.37EB-PEI, was proposed by using experimental data from a miniature isothermal fixed bed reactor system called Autochem. Breakthrough curve tests were conducted at different CO2 concentrations and different temperatures to acquire experimental data under adsorption-dominant conditions. Additionally, temperature programmed desorption (TPD) experiments were carried out for different CO2 concentrations with different starting temperatures to investigate the desorption kinetics. A modified Langmuir kinetic equation was found to provide a satisfactory representation of the adsorption-dominant experimental data, including the long tails. A separate kinetic model was proposed to express the desorption-dominant TPD data. The dynamic effects of the empty volume in the Autochem device on the experimental measurements were rigorously handled through separate empty-volume dynamic tests.

      PubDate: 2017-11-15T18:06:36Z
       
  • Measurement of gas phase characteristics in vertical oil-gas-water slug
           and churn flows
    • Abstract: Publication date: 23 February 2018
      Source:Chemical Engineering Science, Volume 177
      Author(s): Da-Yang Wang, Ning-De Jin, Yun-Feng Han, Fan Wang
      In the present study, gas phase characteristics of oil-gas-water slug and churn flows in a vertical upward pipe with 20 mm inner diameter (ID) are experimentally investigated. We firstly measure the fluctuating signals of a traversable bi-optical fiber probe at different radial positions. The gas phase flow parameter distributions (local gas velocity, local gas holdup) are obtained and the flow structure is uncovered by calculating the series of gas bubble chord lengths at different radial positions. Additionally, in order to describe the flow structure of slug flow, the relative length of the liquid slug, the profile distributions of gas holdup and bubble size in liquid slug are investigated. To understand the nonlinear dynamic characteristics of slug and churn flows, multi-scale cross entropy (MSCE) algorithm is applied to analyze the signals of a high-resolution half-ring conductance sensor and bi-optical fiber probe. The result indicates that multi-scale cross entropy can be an effective tool for validating the measurement of gas phase characteristics by using the traversable bi-optical fiber probe.

      PubDate: 2017-11-15T18:06:36Z
       
  • Computational fluid dynamics simulation of an industrial P. chrysogenum
           fermentation with a coupled 9-pool metabolic model: Towards rational
           scale-down and design optimization
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Cees Haringa, Wenjun Tang, Guan Wang, Amit T. Deshmukh, Wouter A. van Winden, Ju Chu, Walter M. van Gulik, Joseph J. Heijnen, Robert F. Mudde, Henk J. Noorman
      We assess the effect of substrate heterogeneity on the metabolic response of P. chrysogenum in industrial bioreactors via the coupling of a 9-pool metabolic model with Euler-Lagrange CFD simulations. In this work, we outline how this coupled hydrodynamic-metabolic modeling can be utilized in 5 steps. (1) A model response study with a fixed spatial extra-cellular glucose concentration gradient, which reveals a drop in penicillin production rate q p of 18 – 50 % for the simulated reactor, depending on model setup. (2) CFD-based scale-down design, where we design a 1-vessel scale down simulator based on the organism lifelines. (3) Scale-down verification, numerically comparing the model response in the proposed scale-down simulator with large-scale CFD response. (4) Reactor design optimization, reducing the drop in penicillin production by a change of feed location. (5) Long-term fed-batch simulation, where we verify model predictions against experimental data, and discuss population heterogeneity. Overall, these steps present a coupled hydrodynamic-metabolic approach towards bioreactor evaluation, scale-down and optimization.
      Graphical abstract image

      PubDate: 2017-11-15T18:06:36Z
       
  • Local gas holdup and bubble dynamics investigation during microalgae
           culturing in a split airlift photobioreactor
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Aastha Ojha, Muthanna Al-Dahhan
      To make the process of microalgae cultivation for bioenergy, and wastewater and flue gas treatment economically viable, it is important to completely understand the gas–liquid interaction inside photobioreactors in real microalgae cultures completely. Due to limitations of the conventional measurement techniques in the literature, only the overall parameters (such as overall gas holdup and interfacial area) have been studied mostly in air–water systems in the literature. Thus, the variation of local parameters such as local gas holdup and bubble dynamics properties like bubble passage frequency, bubble chord length and velocity, and interfacial area in real culturing systems remains unclear. In this study, these properties were studied at different axial locations inside a split- airlift photobioreactor at superficial gas velocities of 1.0, 2.0, and 2.8cm/s while culturing microalgae Scenedesmus sp. The viscosity of the medium was seen to increase with the optical density of the culture, while the surface tension remained the same throughout the experiment. While, as expected, an increase in superficial gas velocity increased the bubble passage frequency, gas holdup, and interfacial area, the effect of optical density was observed to be the opposite. Over the duration of the experiment, bubble passage frequency in the riser decreased by 62% at 1.0cm/s, 34% at 2.0cm/s, and 25% at 2.8cm/s; the gas holdup in the riser at velocities of 1.0 and 2.0cm/s decreased by 33%, whereas, at 2.8cm/s, it first reached a maximum and then decreased sharply by 29%; the interfacial area in the riser decreased steadily at velocities 1.0 and 2.0cm/s by 40% overall, while that at 2.8cm/s first remained constant at an average of 1.24 and then dropped by 60% at the end of the experiment. While no significant axial variation in the bubble properties was observed in the riser, an axial variation in these properties was observed in the downcomer due to a decrease in the number of bubbles descending through the downcomer. The bubble chord length and bubble velocity distributions became wider at higher superficial gas velocities and higher optical densities. New correlations were developed, accounting for the change in optical density as well as superficial gas velocity, to predict the gas holdup in the riser and at different axial locations in the downcomer.

      PubDate: 2017-11-15T18:06:36Z
       
  • An ethane-trapping MOF PCN-250 for highly selective adsorption of ethane
           over ethylene
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Yongwei Chen, Zhiwei Qiao, Houxiao Wu, Daofei Lv, Renfeng Shi, Qibin Xia, Jian Zhou, Zhong Li
      Energy-saving separation of ethane/ethene (C2H6/C2H4) mixtures is of great importance and challenge. In this work, we reported an iron-based metal–organic framework PCN-250 as a C2H6-selective adsorbent for efficient C2H4 purification from C2H6/C2H4 mixtures. Adsorption isotherms of C2H6 and C2H4 were measured and their adsorption capacities were 5.21 and 4.22mmol/g at 298K and 100kPa, respectively. The adsorption selectivities of C2H6/C2H4 mixtures (1:15 and 1:1, v/v) were in the range of 1.9–4.0 on the basis of ideal adsorbed solution theory (IAST). Meanwhile, its separation performance was also corroborated by the breakthrough experiments, indicating the potential of C2H4 purification from C2H6/C2H4 mixtures, particularly for trapping C2H6 from typical cracked gas mixtures (C2H6/C2H4, 1:15). Compared with C2H4-selective adsorbents through π-complexation interactions, the isosteric adsorption heat of C2H6 on PCN-250 was much lower and thus could require less energy for desorption. Meanwhile, configurational-biased grand canonical Monte Carlo (CB-GCMC) method was employed to well simulate its adsorption behaviors in PCN-250. Simulation results showed that the favorable adsorption sites of C2H6 and C2H4 were distributed at four corners near benzene rings and around the N atoms of PCN-250. Both the pore effect and the van der Waals (vdW) adsorption energy governed the separation of C2H6 over C2H4 for PCN-250, especially at low pressures. Providing that PCN-250 is used as a C2H6-selective adsorbent for purifying C2H4 from C2H6/C2H4 mixtures, this high-performance material can hold great potential for trapping C2H6 from C2H6/C2H4 mixtures.
      Graphical abstract image

      PubDate: 2017-11-15T18:06:36Z
       
  • DEM-SPH study of molten slag trickle flow in coke bed
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Shungo Natsui, Akinori Sawada, Koki Terui, Yusuke Kashihara, Tatsuya Kikuchi, Ryosuke O. Suzuki
      A fully-Lagrangian numerical model was applied for understanding packed bed structures containing non-spherical solids, such as coke, and the high-temperature melt trickle flow characteristics of such beds. Smoothed-particle hydrodynamics (SPH) simulations can track the motion of liquids without discriminating between continuous and dispersed phases, and the extended discrete element method (DEM) is employed as a highly accurate method for simulation of non-spherical solid-particle motion. Based on this model, we carried out large-scale trickle flow simulations using more than 10 million particles, investigated case studies of statistical processing, and evaluated the effects of packed bed formed from various non-spherical coke samples. We found that the pathway that the passing rivulet takes down depends on the structure of the void and the neck size between two voids. If the connecting neck is larger than the capillary length λ = σ / ρ g , the slag will drain. The shape of pathway was related that the solids shape factor which is considered by the projected area in the direction of gravity. Even if cokes with similar size were obtained by sieving, low sphericity cokes block slag flow through channeling voids, i.e., as the projected area of the non-spherical solid shape increased, the liquid hold up showed a tendency to increase.
      Graphical abstract image

      PubDate: 2017-11-15T18:06:36Z
       
  • MnFePSi-based magnetocaloric packed bed regenerators: Structural details
           probed by X-ray tomography
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Alexander Funk, Michael Zeilinger, Anja Miehe, Daniel Sopu, Jürgen Eckert, Florian Dötz, Anja Waske
      Magnetic refrigeration is considered as an alternative to conventional gas-compression-expansion cooling techniques. While the physical properties of magnetocaloric materials have been studied extensively, the question of how to process and shape these materials into active magnetic regenerator (AMR) heat exchangers for application in magnetocaloric cooling devices is less explored. Packed beds made from gas atomized spherical particles offer attractive shaping options to realize an AMR. In this work, we show that X-ray computed tomography (XCT) allows for non-destructive testing of the packed bed magnetic regenerators, including 3D visualization of the internal bed structure, measurement of the particles’ packing density and homogeneity, detection of defects, cracks and interfaces between the layers with different transition temperatures. In this way, XCT can help to understand structural details of fabricated magnetocaloric regenerators and their influence on the performance in a cooling device.
      Graphical abstract image

      PubDate: 2017-11-15T18:06:36Z
       
  • Preparation of chemically uniform and monodisperse microparticles as
           highly efficient solid acid catalysts for aldol condensation
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Jongmin Kim, Si Hyung Jin, Kyoung-Ku Kang, Young-Min Chung, Chang-Soo Lee
      Highly active heterogeneous catalysts are in high demand, but realizing an efficient heterogeneous catalyst with uniform active sites remains challenging. In this study, we present a facile preparation of carboxylic acid-incorporated monodisperse microparticles (COOH-MPs) with uniform active sites and their successful application as an efficient solid acid catalyst for aldol condensation. The micromolding integrated with UV-induced photopolymerization enables one-step preparation of COOH-MPs without any further purification or treatment. The successful fluorescent labeling of the COOH-MPs achieved by EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/n-hydroxysuccinimide (NHS)) chemistry proves that carboxylic acids are uniformly incorporated throughout the COOH-MPs. The microparticle as a solid acid catalyst is applied for aldol condensation and the catalytic performance is compared with that of conventional inorganic solid acid catalysts. The selectivity for jasminaldehyde over the COOH-MPs is higher than that of conventional catalysts, zeolite H-beta (HBEA with different SiO2/Al2O3 ratios). Overall, the results clearly indicate the potential of this new class of chemically uniform and monodisperse microparticle-based solid acid catalysts for aldol condensation. This approach is highly promising for the application to preparations of various solid catalysts due to its reproducibility, tunability and simplicity.
      Graphical abstract image

      PubDate: 2017-11-15T18:06:36Z
       
  • Towards improved predictions for the enzymatic chain-end scission of
           natural polymers by population balances: The need for a non-classical rate
           kernel
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Yong Kuen Ho, Christoph Kirse, Heiko Briesen, Mehakpreet Singh, Chung-Hung Chan, Kien-Woh Kow
      Enzymatic chain-end depolymerization is commonly employed for the transformation of biomass into important products. To date, investigation on the validity of the rate kernel which is critical to model success, has been conveniently avoided. Through a case study with extensive confrontation with experimental data, we uncover this critical relationship by inspecting every minute detail in the mechanistic modelling procedure. Using a newly proposed shape-evolving function for the rate kernel, model calibration reveals that the commonly employed constant rate kernel is inappropriate for modelling the scission step, and that the apparent rate kernel of hydrolysis resembles an endothermic activation energy barrier function. Facilitated by the adoption of this non-classical rate kernel, good predictions are attained by the model at different hydrolysis conditions with a global parameter set. Being the first to predict distributed data, the methodology here serves as a guide for future studies on the enzymatic disruption of polymeric biomass, i.e. for guiding substrate and enzyme structure modifications.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Transient three-dimensional simulation of densification process of carbon
           fibre preforms via chemical vapour infiltration of carbon matrix from
           methane
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Zhepeng Tang, Aijun Li, Tomo Hatakeyama, Hiroki Shuto, Jun-ichiro Hayashi, Koyo Norinaga
      Chemical vapour infiltration (CVI) is widely used for fabricating carbon fibre-reinforced carbon materials for aircraft brake disks. This study aims at developing a numerical simulation method for predicting densification of the material during the CVI. Based on the multi-step reaction and deposition models, including the hydrogen inhibition model of pyrocarbon growth, transient 3D simulations of the CVI using methane as a precursor of the pyrocarbon were carried out via the finite element method coupling the mass transfer (by convection and diffusion) and the evolutive porous structure model with gas-phase and surface chemical reactions. The CVI of two different types of preforms was studied. The pore structure evolution models were derived not analytically but numerically with the aid of a computational tool for visualizing the fibre structures. An acceptable agreement was found between the predicted densification profiles and the experimental data obtained using a laboratory CVI reactor at a temperature of 1343 K, a methane pressure of 30 kPa and a total deposition time of 120 h.

      PubDate: 2017-11-09T10:43:27Z
       
  • Controlled synthesis of graphite oxide: Formation process, oxidation
           kinetics, and optimized conditions
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Chang Li, Yexun Shi, Xi Chen, Dafang He, Liming Shen, Ningzhong Bao
      Graphite oxide (GO) is one of the most extensively studied materials and has been tested for numerous applications due to its unique properties. Nevertheless, a quantitative description of complicated transfer and reaction rates of the oxidation of graphite is still not available, which essentially hinders large-scale production of high-quality GO and other graphene related materials. In this work, GO is prepared from flake graphite (FG) by a modified Hummers method. Size and color evolutions of time-dependent complementary domains, i.e. the starting GO domain and the remaining FG domain, are monitored during the entire oxidation process. The oxidation of FG in acidic oxidizing medium can be interpreted as a contracting area process controlled by phase boundary. Reaction rate constant (k) and kinetic parameters (Ea , ln A) are obtained after a systematic investigation of the influence of reaction temperature, concentration of sulfuric acid, and oxidizing agent on the oxidation, with the aid of R2 mathematical model. Using the kinetic results, the oxidation process and the conversion rate from FG to GO thus become controllable. Both intermediate products and final GO products are studied using XRD, TGA, and XPS to reveal the oxidation mechanism. The degree of oxidation of FG and the content of major functional groups on the surface of products can thus be optimized. Our research results are valuable to understanding fundamental mechanism of graphite oxidation and to achieving industrial production of high-quality GO with controllable degree of oxidation and tunable proportion of oxygen-containing functional groups for a variety of applications.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Evolution of flow regimes in non-Newtonian liquids under gas sparging
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Qian Xu, Pradipto K. Bhattacharjee, Doug Allitt, Nicky Eshtiaghi, Rajarathinam Parthasarathy
      This paper provides experimental evidence supporting the idea that the transition to turbulent flow is governed by the ratio of the specific power input (SPI) and the term G/λ, where G is the viscoelastic modulus of the liquid and λ is the relaxation time, in a vessel containing a fluid agitated by sparged gas (air) at low superficial gas velocities. This finding provides a method for judging the flow regime within a vessel a priori using a nondimensional quantity and can be used as a scale for decision-making in cases where real-time visual analysis is not possible. While the work reported below is motivated by anaerobic digestion of wastewater sludge, the results are obtained using model liquids and should, therefore, have wide application in chemical process engineering, such as CFD simulation of mixing in viscoelastic fluids and mixing in fermentation processes.

      PubDate: 2017-11-09T10:43:27Z
       
  • Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for
           NH3-SCR (I): The impact of 950 °c hydrothermal aging time
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Dequan Fan, Jun Wang, Tie Yu, Jianqiang Wang, Xiaoqian Hu, Meiqing Shen
      The hydrothermal stability of Cu/SAPO-34 catalysts under different treatment time (3 h, 6 h, 12 h) at 950 °C has been investigated to understand their framework collapse and deactivation mechanism for NO reduction by ammonia selective catalytic reduction (NH3-SCR). It was seen that SCR activities declined dramatically after 12 h aging, and XRD results showed this treatment led to crystallinity decline since 3 h. Furthermore, zeolites crystal started to transform into SiO2 and AlPO4 phase since 6 h. NMR results further proved the formation of SiO2 and AlPO4·NH3-TPD and ex-situ DRIFTS results revealed the breakage of Si-OH-Al bonds and the decline of the number of Brønsted acid sites, meanwhile, H2-TPR and EPR results proved that the number of Cu2+ species decreased and the location of Cu2+ species changed after this treatment, which were mainly responsible for declined SCR reaction rates.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Variations in the molecular weight response of anionic polyacrylamides
           under different flocculation conditions
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Allan Costine, James Cox, Shaun Travaglini, Alex Lubansky, Phillip Fawell, Holger Misslitz
      The influence of applied mixing (intensity and duration), solids concentration, and liquor chemistry on the molecular weight (MW) response of seven anionic (30%) polyacrylamides was investigated in the flocculation of standard kaolin slurry at pH 8. Continuous flocculation was achieved in a Couette mixing device (CSIRO Shear Vessel) with a vertical flow-through arrangement allowing operator-independent settling rate measurements to be made under tightly controlled mixing conditions. It was found that the relative performance of the flocculants was strongly dependent on the hydrodynamic conditions prevailing during flocculation. The lower MWs gave a more dosage-effective response under mild mixing, producing denser, faster-settling aggregates than equivalent sizes produced with the higher MWs. Conversely, the larger sizes created by the higher MWs gave access to faster settling rates under intense mixing, except in the instance where polymer size and concentration led to chain entanglements. Sodium cations (<0.01 M) in the slurry favoured some degree of particle coagulation, whereas calcium cations had an adverse effect on settling rates even at low concentrations (<0.002 M), with the effects of a reduced bridging capacity most apparent in the lower MWs. The results advance the fundamental understanding of how chain length can substantially alter inter-particle bridging behaviour under different conditions, and thus provide a more robust basis for enhanced dewatering of clay suspensions through flocculant MW selection.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Selective protein quantification for preparative chromatography using
           variable pathlength UV/Vis spectroscopy and partial least squares
           regression
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Nina Brestich, Matthias Rüdt, Daniel Büchler, Jürgen Hubbuch
      In preparative protein chromatography, broad dynamic ranges of protein concentrations as well as co-elution of product and impurities are common. Despite being the standard in biopharmaceutical production, monitoring of preparative chromatography is generally limited to surrogate signals, e.g. UV absorbance at 280 nm. To address this problem, variable pathlength (VP) spectroscopy in conjunction with Partial Least Squares regression (PLS) was used to monitor preparative chromatography. While VP spectroscopy enabled the acquisition of absorbance data for a broad concentration range, PLS modelling allowed for the differentiation between the protein species. The approach was first implemented for monitoring the separation of lysozyme from cytochrome c at an overall loading density of 92 g/l. The same method was then applied to the polishing step of a monoclonal antibody (mAb) at 40 g/l loading density. For PLS model prediction of the mAb monomer and the high molecular weight variants (HMWs), the root mean square error (RMSE) was 1.07 g/l and 0.42 g/l respectively. To demonstrate the usability of the approach for in-line control, pooling decisions for both separation problems were subsequently taken based on the computed concentrations or thereof derived purities. In summary, VP spectroscopy in conjunction with PLS modelling is a promising option for in-line monitoring and control of future chromatography steps at large scale.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Vapor pressure, vapor-liquid equilibria, liquid-liquid equilibria and
           excess enthalpy of the system consisting of isophorone, furfural, acetic
           acid and water
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Olga Ershova, Juha-Pekka Pokki, Anna Zaitseva, Ville Alopaeus, Herbert Sixta
      In this work, the phase equilibria of the system comprised of isophorone, furfural, water and acetic acid were studied from the viewpoint of the extraction process. Equilibrium vapor pressure of pure isophorone was measured at sub-atmospheric pressure. Isobaric (at 40 kPa) isophorone-furfural vapor-liquid equilibria, the excess enthalpy of isophorone-furfural mixture (at 323 K) and isophorone-acetic acid vapor-liquid equilibria (from 322 K to 342 K) were investigated and compared to the available literature data. Liquid-liquid equilibria of systems comprised of isophorone-furfural-water (from 303 K to 343 K) were measured for the first time. The experimental results of this study and the literature values were utilized for optimizing the parameters for UNIQUAC model. The model was validated against the measured liquid-liquid equilibrium of the quaternary system isophorone-furfural-acetic acid-water (from 298 K to 343 K). Isophorone was found to be a favorable solvent for furfural extraction from its aqueous solutions.

      PubDate: 2017-11-09T10:43:27Z
       
  • Thermodynamic prediction of the solvent effect on a transesterification
           reaction
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Max Lemberg, Reinhard Schomäcker, Gabriele Sadowski
      This work focuses on the thermodynamic prediction of solvent effects on the transesterification of butyl acetate with ethanol to butanol and ethyl acetate in the solvent heptane at 293.15 K and 303.15 K. Both, the reaction equilibrium and the reaction kinetics have been investigated experimentally by Schmidt et al. (1999). They found that the solvent heptane does not affect the reaction equilibrium but significantly influences the reaction kinetics. They described the solvent effect on the reaction kinetics by empirically correlating the experimentally-observed apparent rate constants with the dielectric constants of the different reaction mixtures. In this work we re-evaluated the experimental data and now present a thermodynamic approach to consistently predict the solvent effect on both, the reaction equilibrium and the reaction kinetics. Accounting for the activity coefficients of the reactants/products obtained from the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) allowed for considering the interactions of the reactants/products among themselves and also with the solvent heptane. Accounting for those, it is shown that the solvent effect on the reaction equilibrium as well as on the reaction rate can even be predicted in very good agreement with the experimental data.

      PubDate: 2017-11-09T10:43:27Z
       
  • Direct numerical simulation of fluid flow and mass transfer in dense
           fluid-particle systems with surface reactions
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Jiangtao Lu, Saurish Das, E.A.J.F. Peters, J.A.M. Kuipers
      In this paper, an efficient ghost-cell based immersed boundary method is introduced to perform direct numerical simulation (DNS) of mass transfer problems in particulate flows. The fluid-solid coupling is achieved by implicit incorporation of the boundary conditions into the discretized momentum and species conservation equations of the fluid phase. Taking the advantage of a second order quadratic interpolation scheme utilized in the reconstruction procedures, the unique feature of this ghost-cell based immersed boundary method is its capability to handle mixed boundary conditions at the exact position of the particle surface as encountered in systems with interplay between surface reactions and diffusion. A fixed Eulerian grid is used to solve the conservation equations for the entire computational domain. Following a detailed verification of the method in the limiting case of unsteady molecular diffusion without convection, we apply our method to study fluid-particle mass transfer for flow around a single sphere and a dense stationary array consisting of hundreds of spheres over a range of Damköhler numbers.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Study on the meniscus-induced motion of droplets and bubbles by a
           three-phase Lattice Boltzmann model
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Bei Wei, Haibo Huang, Jian Hou, Michael C. Sukop
      In contrast to typical applications of the pseudopotential Lattice Boltzmann model to two components, quantitative validations and applications for three-component Shan-Chen model are performed here. First, the qualitative and quantitative validations for the following three cases were performed, i.e., three-phase separation, meniscus-induced bubble movement, and the three-phase layered flow. A scheme to control the simulated contact angle of droplets on the interface is provided for the three fluid phase Lattice Boltzmann model. The effects of droplet shape, the strength of gravity, droplet size, and meniscus curvature for the spontaneous motion of droplets and bubbles are investigated in detail. It is found that without gravity, droplets tend to move to the wall on a concave upwards meniscus when they have a big “head” and a small “belly”. Gravity may enhance rather than inhibit the motion towards the wall when the density of the droplet or bubble is relatively small. Finally, smaller droplet size and larger meniscus curvatures enhance the spontaneous movement towards a wall. The conclusions are relevant to practical applications such as water treatment, oil spill remediation, and droplet-based microfluidics.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Evolution of mass distribution in walls of rigid polyurethane foams
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Pavel Ferkl, Iveta Kršková, Juraj Kosek
      In this work, we describe a theoretical model for the simulation of reactive foaming of polyurethane (PU) consisting of three parts – reaction kinetics, foam expansion and wall evolution, which are coupled together. The advantage of this approach is that it provides comprehensive details about the development of PU foam – from the evolution of temperature and foam density to morphology features like bubble size, wall thickness and strut shape at the same time. The performance of the model is evaluated by analysing the model predictions for realistic process conditions and comparing to experimental data. It is demonstrated that the increased viscosity of the reaction mixture will lead to foams with thicker walls. The presented model can serve as a useful tool for the optimization of PU foaming process.

      PubDate: 2017-11-09T10:43:27Z
       
  • Three-dimensional simulation of droplet dynamics in planar contraction
           microchannel
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Van Thanh Hoang, Jiseok Lim, Chan Byon, Jang Min Park
      In droplet-based microfluidic systems, microchannel design plays a primary role in transport and manipulation of liquid droplets. The objective of this paper is to investigate dynamics of a droplet in planar contraction microchannel via three-dimensional numerical simulation and theoretical analysis. In particular, this study characterizes three regimes of the droplet dynamics, namely, trap, squeeze and breakup, depending on capillary number (Ca) and contraction ratio (C). In addition, theoretical models have been proposed to describe transitions from one to another regime as a function of Ca and C. For the transition from trap to squeeze, the critical capillary number (CaIc) was found to follow CaIc = a(CM−1), whereas the critical capillary number (CaIIc) of transition from squeeze to breakup corresponds to CaIIc = c1 C −1. Furthermore, details of the droplet dynamics along downstream of the contraction have been explored as well to depict deformation, retraction and/or breakup of the droplet. The present results would be useful guidelines in designing contraction microfluidic channel for precise control and manipulation of droplets.

      PubDate: 2017-11-09T10:43:27Z
       
  • Breakup dynamics for droplet formation in shear-thinning fluids in a
           flow-focusing device
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Wei Du, Taotao Fu, Yingfeng Duan, Chunying Zhu, Youguang Ma, Huai Z. Li
      The breakup dynamics of the dispersed thread for droplet formation in shear-thinning fluids in a flow-focusing device was highlighted. The breakup process of the shear-thinning dispersed thread could be divided into four stages: the droplet growth stage and the squeezing stage, both of them are dominated by the squeezing pressure, the stretching stage controlled by the viscous stresses of dispersed phase and the surface tension, and the pinch-off stage controlled by the viscous stresses of both phases and the surface tension. The breakup dynamics of the dispersed thread for the shear-thinning fluids in each stage is very similar to that of the constant viscosity Newtonian liquids, signifying that the breakup is almost unaffected by the shear-thinning rheological properties.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • On comparison of the sharp-interface and diffuse-interface level set
           methods for 2D capillary or/and gravity induced flows
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Javed Shaikh, Atul Sharma, Rajneesh Bhardwaj
      The present work is on comparison of numerical-methodology as well as performance of the two types of level set methods (LSMs): sharp-interface and diffused-interface. The numerical-methodology along with mathematical-formulation are presented in-detail for relatively recent ghost fluid method based sharp-interface level-set-method (SI-LSM); and compared with the methodology for the traditional diffuse-interface level-set-method (DI-LSM) as well as an improved diffuse-interface dual-grid-level-set-method (DI-DGLSM). Two different types of surface models are considered: continuum surface force (CSF) and sharp surface force (SSF) model; CSF model for the DI-LSM and SSF model for the SI-LSM. The SI-LSM considers the physically realistic sudden variation of the thermo-physical property across the sharp-interface while DI-LSM considers a smoothened value of the properties across the numerically diffused-interface. For solving the pressure Poisson equation in the SI-LSM, a finite volume method based generic formulation is proposed and its implementation-details are presented. For the SI-LSM as compared to DI-LSM and DI-DGLSM, the relative performance study is presented on four reasonably different two-phase problems: surface-tension model induced unphysical flow for a static water droplet, collapse of a water-column in air, falling of a water-droplet in air, and coalescence of an ethanol-droplet over a pool of ethanol in air. For the performance study on various problems, a comparison of the results obtained by the three types of LSMs (SI-LSM, DI-LSM and DI-DGLSM) and various other numerical methods in the literature are presented. SI-LSM as compared to DI-LSM and DI-DGLSM is shown to substantially reduce the unphysical spurious velocity and results in better accuracy on the same grid size.

      PubDate: 2017-11-09T10:43:27Z
       
  • Pressure equalization approach for flow uniformity in microreactor with
           parallel channels
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Ketan Madane, Amol A. Kulkarni
      Numbering-up using parallel channels helps to achieve higher processing capacity while retaining the advantages of microreactors. However it may also lead to non-uniformity in flow across all the channels. Here we report the CFD simulations and experimental observations on the extent of uniformity in the flow from an assembly of several parallel channels. In the conventional parallel channel geometry, smaller channel size (<300 m) as well as higher fluid viscosity is seen to give better flow uniformity. Inequality in pressure distribution at the inlet of a large number of parallel channels is overcome by having two ‘pressure equalization slots’ at an equal distance from inlet and outlets that open in the respective manifolds. Having such an arrangement helped to reduce the standard deviation in the flow by almost 90% when compared to the conventional geometry. However the modification was seen to increase the extent of back mixing to some extent.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Effect of gas sparger design on bubble column hydrodynamics using pure and
           binary liquid phases
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Giorgio Besagni, Lorenzo Gallazzini, Fabio Inzoli
      It is known that the fluid dynamics and transport phenomena in bubble columns depend mainly on the bubble column design (i.e., the column diameter, aspect ratio, and gas sparger openings) and the liquid phase properties. In this communication, we contribute to present-day discussion through an experimental study concerning the combined effects of the gas sparger design and liquid phase properties on both the gas holdup and the main flow regime transition. The experimental study concerning gas holdup measurements was conducted in a large-diameter and large-scale bubble column (with a height of 5.3 m and inner diameter of 0.24 m) operated in the batch mode. Air was used as the dispersed phase (using gas superficial velocities in the range 0.004–0.20 m/s), and various water–monoethylene glycol (MEG) solutions were employed as binary liquid phases. The water–MEG solutions tested have viscosities between 0.9 mPa·s and 7.97 mPa·s, densities between 997.086 kg/m3 and 1094.801 kg/m3, and surface tension between 0.0715 N/m and 0.0502 N/m. Two gas spargers were tested: (a) a spider sparger (“coarse gas sparger”) and (b) a needle sparger (“fine gas sparger”). The former produced a poly-dispersed homogeneous flow regime resulting in a concave gas holdup curve, whereas the latter produced a mono-dispersed homogeneous flow regime resulting in an S-shaped gas holdup curve. It was observed that the mono-dispersed bubble size distribution stabilized the homogeneous flow regime. The addition of MEG produced different effects depending on the gas sparger design. The addition of MEG in the “coarse gas sparger” configuration produced what is usually referred to as “dual effect of viscosity”: depending on the MEG concentration, the homogeneous flow regime was stabilized/destabilized, and thus, the gas holdup increased/decreased. Conversely, the addition of MEG in the “fine gas sparger” changed the shape of the gas holdup curve from an S-shape to concave, thus rendering it similar to the ones produced by “coarse gas sparger”. We speculate that viscous solutions reduce the influence of the inlet conditions in large-diameter and large-scale bubble columns; this is a matter of future research.

      PubDate: 2017-11-09T10:43:27Z
       
  • Effect of surfactant on emulsification in microchannels
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Nina M. Kovalchuk, Evangelia Roumpea, Emilia Nowak, Maxime Chinaud, Panagiota Angeli, Mark J.H. Simmons
      Drop formation in a microfluidic flow-focusing device (cross-junction) was studied in absence and presence of one of two ionic surfactants. Four different flow regimes: squeezing, dripping, jetting, and threading were observed in line with existing literature. The effect of surfactant on the transition between flow regimes was shown to depend upon the value of critical micelle concentration and correlates with dynamic surface tension. Drop length in the channel increased as the ratio of flow rate of dispersed to continuous phase, φ, increased. For drops smaller than the channel width, the increase was slow, proportional to φ0.1, yet was much faster, proportional to φ, for larger drops. In contradiction to the expected stabilisation of drops by surfactant, surfactant-laden drops larger than the channel height coalesced inside the channel at a higher rate than surfactant-free drops. It is proposed that the coalescence is caused by the electrostatic attraction due to surfactant redistribution under the high shear stresses near the wall of the channel.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Analysis of electroosmotic flow and Joule heating effect in a hydrophobic
           channel
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): A.K. Nayak, A. Haque, B. Weigand
      In this paper, a mathematical model has been developed to analyze the fluid flow and heat transfer effect in a hydrophobic microchannel filled with a power law fluid. The effects of Joule heating, thermal radiation and velocity slip boundary conditions are analyzed by considering different slip parameters, EDL thickness, pressure gradient and flow behavior indices. The analytical expression for fluid flow and heat transfer have been derived in terms of the flow governing parameters based on the Debye-Huckel linearizing principle. Depending on the experimental existing flow behavior index, the analytical solutions are obtained in closed form where as numerical results are presented for general parametric values. The impact of slip velocity parameters in terms of a flow enhancement factor ( E fb ) , is studied to obtain the average flow velocity variation in a hydrophobic microchannel compared to a plane microchannel. The pressure assisted flow for pseudo-plastic (shear thinning) fluids achieve maximum velocity as compared to dilatant (shear thickening) fluids. The study finds that increase in thermal radiation minimizes heat transfer rate close to the hydrophobic wall, plays a vital role for the therapeutic treatment of hyperthermia (to understand the effect of heat transfer due to electric potential). It is also observed that Joule heating parameters enhance the heat transfer rate for classical Newtonian/non-Newtonian fluids for decrease in power indices and pressure gradient.

      PubDate: 2017-11-09T10:43:27Z
       
  • Micromixing by two-phase hydrodynamic focusing: A 3D analytical modeling
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Arman Sadeghi
      Rapid and efficient mixing is crucial in microfluidic devices. The two-phase hydrodynamic focusing has already been shown to be a flexible method of micromixing. In this method, the sample stream composed of solute and solvent is squeezed between two sheath flows of a highly viscous fluid so as to reduce the diffusion path. The main challenge in modeling the associated transport phenomena is the difference between the viscosities and diffusivities of the sample and sheath flows. In this paper, 3D analytical solutions are presented for solute transport in two-phase focusing micromixers, regarding the sample and sheath flows as a single domain of variable physical properties. The model is shown to be able to capture the change of the concentration gradient at the sample/sheath interfaces. The results demonstrate that the mixing length can be reduced significantly by employing more viscous sheath flows while even having more values of efficiency, defined as the ratio of the solutes remaining in the sample flow to the total solutes. Although smaller mixing lengths may also be obtained by increasing the sheath flow rate in single-phase focusing, it is accompanied by sever reductions in efficiency, revealing that the single-phase focusing is not an efficient mixing tool.

      PubDate: 2017-11-09T10:43:27Z
       
  • Dynamic capillary phenomena using Incompressible SPH
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Prapanch Nair, Thorsten Pöschel
      Grid based fluid simulation methods are not able to solve complex non-linear dynamics like the rupture of a dynamic liquid bridge between freely colliding solids–an exemplary scenario of capillary forces competing with inertial forces in engineering applications–using a monolithic formulation for the solid and liquid phases present. We introduce a new Incompressible Smoothed Particle Hydrodynamics method for simulating three dimensional fluid-solid interaction flows with capillary (wetting and surface tension) effects at free surfaces. This meshless approach presents significant advantages over grid based approaches in terms of being monolithic and in handling interaction with free solids. The method is validated for accuracy and stability in dynamic scenarios involving surface tension and wetting. We then present three dimensional simulations of crown forming instability following the splash of a liquid drop, and the rupture of a liquid bridge between two colliding solid spheres, to show the method’s advantages in the study of dynamic micromechanical phenomena involving capillary flows.

      PubDate: 2017-11-09T10:43:27Z
       
  • Modeling of convective turbulent heat transfer of water-based Al2O3
           nanofluids in an uniformly heated pipe
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Ghofrane Sekrani, Sébastien Poncet, Pierre Proulx
      Turbulent convective heat transfers of Al 2 O 3 -water nanofluid flowing in a circular tube subjected to an uniform wall heat flux are numerically investigated using different turbulence models. Four nanoparticle volume concentrations φ up to 2 % are considered for bulk Reynolds numbers within the range 3000 ⩽ Re ⩽ 20 , 000 . The effects of the nanoparticle concentration and the Reynolds number on the Nusselt number and friction factor are reported. Two different numerical approaches including the single-phase and the mixture two-phase models with variable thermophysical properties are favorably compared to experimental results obtained from the literature for low nanoparticle concentrations ( φ ⩽ 0.5 % ). The results at a higher volume fraction φ = 2 % show the necessity to use a mixture model. Eight turbulence models in their low-Reynolds number formulation are also compared to assess their ability to predict the effect of turbulence on the convective heat transfer. The SST k- ω model was found to perform the best with errors in terms of the average Nusselt number and friction coefficient of 0.44 % and 1.82 % respectively. On the contrary, the linear pressure-strain Reynolds Stress Model completely failed to provide the good values with discrepancies of 41.91 % and 133.54 % , respectively. Finally, the benefit of using this nanofluid is discussed regarding four merit criteria.

      PubDate: 2017-11-09T10:43:27Z
       
  • Hydrodynamics and flow mechanism of foam column Trays: Contact angle
           effect
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Peng Yan, Xingang Li, Hong Li, Xin Gao
      Wettability has significant influence on fluid flow inside foam ceramics. Foam SiC valves with various wettability were prepared by a facial bottom-up strategy. Subsequently, pressure drop, weeping and gas distribution were studied. Results indicate that pressure drop decreases remarkably with increasing contact angle (CA), 43% at most; weeping rate presents a peak at CA<90°but monotonous decrease at CA>90°; gas distribution becomes more uniform with increasing CA at small F-factor but presents obvious boundary effect at large F-factor. To illustrate the CA effect, we propose a new strategy for pressure drop decomposition, introducing the fourth part called CA-induced pressure drop by modifying classical three-component strategy, which also catalyzes a new pressure drop measuring strategy. In the meanwhile, the mathematical model to predict pressure drop is proposed and shows good agreement with experiments. Moreover, process model to illustrate the mechanism is proposed based on interfacial phenomena, force analysis and flow patterns.

      PubDate: 2017-11-09T10:43:27Z
       
  • Non-spherical solid-non-Newtonian liquid fluidization and ANN modelling:
           Minimum fluidization velocity
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Samit Bikas Maiti, Sudipta Let, Nirjhar Bar, Sudip Kumar Das
      Experiments have been carried out to determine the minimum fluidization velocity for sand particles of irregular shape and size using pseudoplastic liquids in different Perspex columns. The effect of different operating parameters, like column diameter, particle size and shape, rheological properties of the liquid on minimum fluidization velocity has been investigated. It has been observed that as sphericity of the particle decreases, minimum fluidization also decreases. Empirical correlation has been developed to predict the minimum fluidization velocity as a function of physical and dynamic variable of the system. Statistical analysis of the correlation suggests that is of acceptable accuracy. Applicability of the artificial neural network modelling using gradient descent and Levenberg-Marquardt algorithm have also been successfully tested.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Numerical simulation of struvite crystallization in fluidized bed reactor
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Xin Ye, Yongchuan Gao, Jingcai Cheng, Dongyuan Chu, Zhi-Long Ye, Shaohua Chen
      A numerical model has been developed for struvite-crystallization in a fluidized bed reactor (FBR). For the first time, the flow field and crystal size distribution (CSD) are simultaneously obtained via solving the model that couples computational fluid dynamics (CFD) and population balance equation (PBE). The model was first verified based on the experimental data, and used to explore the influences of operating conditions and reactor geometry. The results showed that the predictions were in good agreement with the experimental observations, giving similar phosphorus removal trend. The predicted supersaturation levels, solid concentrations, and CSDs were found to be strongly dependent on the recycle ratio, pH, and inflow rate. Moreover, the split module was considered better as compared with the traditional integrated module in terms of the supersaturation control. The proposed CFD–PBE modeling framework is thus considered to be a useful tool for performance evaluation and geometry optimization of struvite crystallization.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Formation mechanisms of solid in water in oil compound droplets in a
           horizontal T-junction device
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Dawei Pan, Meifang Liu, Fang Li, Qiang Chen, Xiangdong Liu, Yiyang Liu, Zhanwen Zhang, Weixing Huang, Bo Li
      The formation mechanisms of S/W/O compound droplets in a horizontal T-junction device was investigated. According to the capillary number, Ca , of a continuous phase and the ratio, R, given by R = Q main/Q side, the formation mechanisms which are the double-encapsulation, squeezing regime, dripping-like regime, and the jetting-like regime can be distinguished. In the squeezing regime, the lag of the PS shell relative to the W phase results in a different squeezing stage, in which the neck thickness decreases firstly and then increases because of the limited deformation of the W/O interface by the PS shell. After the PS shell totally intrudes into the main channel, the neck thickness decreases again. In the dripping-like regime, the gap distance decreases linearly with the entry of the PS shell into the main channel. Therefore, compared with W/O droplets in dripping regime, the dominant force that breaks off the neck remains to be the pressure drop force, and not the shearing force, because of the comparatively large diameter of the PS shell to that of the channel. A high Ca and low R contribute to the formation of the jetting-like regime, in which the inertia force and shearing force contribute to the formation of a long tip because of the large flow rates in the main and side channel. In addition, regimes in the flow pattern diagram dependent on Ca and R are obtained.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Mixing and orientation behaviors of cylindrical particles in a mixing
           layer of an Oldroyd-B fluid
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Jianzhong Lin, Yelong Wang, Peijie Zhang, Xiaoke Ku
      The effect of Stokes number, Weissenberg number, particle aspect ratio and particle-to-fluid density ratio on the mixing and orientation distributions of cylindrical particles in a mixing layer of an Oldroyd-B fluid is numerically studied using the pseudo-spectral method and Runge-Kutta method. The results show that the particles with annular orbit will rotate around the large vortex center and mix into the core of the vortex, while the particles with wavy orbit do not involve the mixing process. The particles with a small Stokes number are distributed homogenously and mixed thoroughly, whereas the particles with a large Stokes number are poorly mixed and centrifugalized to the edge of the vortex. The range of mixing area is decreased with increasing Stokes number. The initial orientation of the particles has a weak effect on its motion orbit. The roll-up of mixing layer drives the particles to the edge of the vortex, the particle mixing becomes worse with increasing Stokes number and particle aspect ratio, and with decreasing the Weissenberg number. When the Weissenberg number is small, and the Stokes number and particle aspect ratio are large, a little more particles orient towards the vorticity axis. With increasing the Weissenberg number, and decreasing the Stokes number and particle aspect ratio, more particles align themselves on the flow-gradient plane. The Stokes number has a stronger effect on the particle mixing than on the orientation distributions, whereas the particle aspect ratio and particle density have a stronger effect on the orientation distributions than on the particle mixing. The Weissenberg number has a stronger effect on the orientation distributions than the particle aspect ratio and Stokes number. The particles drift along the spanwise direction mostly take place at the initial stage, and both maximum and average drift distance finally reach a stable value.

      PubDate: 2017-11-09T10:43:27Z
       
  • Evaporation excites temporal sequence of resonant modes in a sessile
           droplet perturbed at constant frequency – Insights into the universal
           dynamics of mode transitions
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Apratim Sanyal, Saptarshi Basu
      A sessile droplet excited at a constant frequency exhibits a temporal sequence of interface modes when allowed to evaporate. Evaporation tunes the droplet to resonate at different modes in a descending order. The life of each mode spans over a transition stage from the onset of its own resonance to that of the next lower order mode. Mode lifetime during the evaporation period of any droplet has been found to decrease in a power law fashion both theoretically and experimentally when higher driving frequencies are considered. Such dynamics are driven by both evaporation and interface oscillations, the latter being governed by the dispersion relation of one dimensional capillary wave. The natural excitation of sequential mode resonances in the present case is governed by a tuning parameter. Variation of this parameter by evaporation is analogous to external frequency sweep in non evaporating droplets to detect similar mode resonances. The dynamics of transition stage corresponding to each mode is characterized by a second parameter denoted as mode transition parameter. The transition stage (higher to lower order) is initially fast but slows down close to the resonance of lower order mode. Theoretical expressions of mode lifetimes and the tuning parameter have been derived based on reasonably valid assumption of constant static contact angle (a measure of the contact angle of the unperturbed hypothetical droplet shape in an oscillation cycle). An approximate linear relation has been established between detuning (complement of the tuning parameter) and mode transition parameters which governs the dynamics of the transition stage. The experimental data corresponding to the detuning and mode transition parameters show universal merging for all excitation frequencies. The experimental data also follows the proposed theoretical linear trend but deviates towards the later part of the transition stage. Such deviations have been attributed to neglecting higher order terms and possible viscous damping from boundary layer at the substrate. Even then the universality of mode transition across all frequencies is maintained throughout the evaporative lifetime.

      PubDate: 2017-11-09T10:43:27Z
       
  • LES and PIV investigation of turbulent characteristics in a vessel stirred
           by a novel long-short blades agitator
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Xiang Pan, Li Ding, Peicheng Luo, Hua Wu, Zheng Zhou, Zhibing Zhang
      This study focuses on the macroscopic characteristics of the turbulent flow in a vessel equipped with a newly developed long-short blades (LSB) agitator. After validation by PIV experiments, the LES method using dynamic kinetic energy sub-grid scale model, coupled with sliding mesh approach, was used to investigate the flow patterns, the axial and radial flow rates, turbulent dynamic energy distribution, and the power number in the vessel with the LSB agitator at the liquid height, H/T = 1.0 and 1.5, respectively. It is found that the turbulent characteristics are substantially different from those of the conventional agitators. The short blades of the LSB agitator generate a strong axial up-flow in the center, which interacts with the dominant radial motion of the long blades, leading to formation of multiple vortexes along the axis. The direction of the flow in the vortex above the short blades is opposite to that below the short blades, which is completely different from the classical Rushton turbine. Effective mass exchange between the axial and radial flows occurs nearly in the entire vessel. Compared with the conventional agitators, the LSB agitator can achieve high mixing performance and much better homogeneity in the distribution of the turbulent kinetic energy. The effect of the liquid height on the power number and the specific power consumption was also discussed.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Effect of the contact angle on the morphology, residence time distribution
           and mass transfer into liquid rivulets: A CFD study
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Daniel Sebastia-Saez, Sai Gu, Marco Ramaioli
      Droplets and rivulets over solid surfaces play an important role in a number of engineering applications. We use a Computational Fluid Dynamics model consisting in a smooth inclined plate to study the effect of the contact angle on the morphology, residence time and mass transfer into liquid rivulets. Measurements of the contact angle—using the sessile drop method—between aqueous monoethanolamine solutions and two commercial surfaces used for gas separation, are introduced as boundary condition. Reducing the contact angle from 60 ° to 20 ° flattens the rivulet, increasing the gas-liquid interface area by 85%. The cumulative residence time broadens, with an increase of 12% in τ 10, and of 37% in τ 90. There is consequently, a theoretical increase of 68% in the total mass transfer rate. A sensible design of the liquid-solid interaction is therefore crucial to good mass transfer performance.

      PubDate: 2017-11-09T10:43:27Z
       
  • Modelling and numerical simulation of coupled transport phenomena with
           phase change: Layer evaporation of a binary mixture
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Sebastian Rieks, Eugeny Y. Kenig
      In spite of intense research on coupled transport phenomena in fluid systems, their rigorous modelling and simulation still remains a challenge, especially if a phase change is involved. In this case, the mathematical description becomes particularly interrelated and complex. In the literature, usually only few selected aspects of such problems are considered, e.g. in isothermal or one-component systems. In this work, a more holistic approach is suggested comprising promising concepts available in the literature. The resulting model and relevant code for the Computational Fluid Dynamics (CFD)-simulation of momentum, total mass, species, and heat transfer in two-phase binary systems are free of any heuristic or empirical parameters and thus are applicable to a wide range of problems. Several one-dimensional simulation cases are considered to provide a first validation of the model.

      PubDate: 2017-11-09T10:43:27Z
       
  • A novel multiscale theoretical model for droplet coalescence induced by
           turbulence in the framework of entire energy spectrum
    • Abstract: Publication date: 2 February 2018
      Source:Chemical Engineering Science, Volume 176
      Author(s): Shenggao Gong, Luchang Han, He'an Luo
      This work mainly focused on the droplet coalescence induced by turbulence. Two kinds of interaction mechanisms between turbulent eddies and droplets were proposed, and the corresponding coalescence model for each mechanism has also been proposed by counting the number of collisions that can lead to coalescence directly. Most of previous coalescence models only considered the contribution of the turbulent eddies of size equal to the size of droplets since the droplet velocity was assumed to be equal to the velocity of turbulent eddies of same size. In contrast, the contribution of multiscale turbulent eddies (i.e. turbulent eddies with various sizes, not just the turbulent eddies of size equal to the size of droplets) to the coalescence of droplets of given sizes was considered in the proposed model. This work also simulated the coalescence in the framework of entire energy spectrum. Simultaneously, the influences of the average collision free path between droplets and turbulent eddies as well as the lifetime of turbulent eddies on the coalescence were considered. Furthermore, this work proposed a novel second-order longitudinal structure function, which showed a good agreement with the results of direct numerical simulation. Finally, the predicted droplet size distributions of the proposed model were in agreement with experimental data.
      Graphical abstract image

      PubDate: 2017-11-09T10:43:27Z
       
  • Improving the thermo-tolerance of yeast base on the antioxidant defense
           system
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Ke Xu, Liman Gao, Jalees Ul Hassan, Zhiping Zhao, Chun Li, Yi-Xin Huo, Guiyan Liu
      Heat stress in yeast limits productivity in the industrial production of bio-ethanol. One promising way for enhancing yeast resistance to heat is to strengthen the antioxidant defense system. Herein, we developed an artificial antioxidant defense system and used it to improve the thermo-tolerance of yeast for the first time. Engineered strains not only exhibited high-performance on tolerance to high temperature but also effectively improved the ethanol yield. A-SOD2-TTHA1300 showed the highest ethanol yield, 61.4 g/L at 60 h, which is increased by 66% compared with the control. Furthermore, we explored the damage mechanism of cells under heat stress and oxidative stress by detection of mitochondria and cell membrane integrity. These results together demonstrated the great potential of artificial antioxidant defense system in improving the thermo-tolerance in yeast.

      PubDate: 2017-10-18T09:45:08Z
       
  • Influence of micromixing time and shear rate in fast contacting mixers on
           the precipitation of boehmite and NH4-dawsonite
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Robin Lafficher, Mathieu Digne, Fabien Salvatori, Malika Boualleg, Didier Colson, François Puel
      The textural properties of γ-alumina catalyst supports largely depend on the solid properties of their precursors. Precipitation in fast contacting mixers of two precursors, boehmite and NH4-dawsonite, were investigated in order to obtain different and enhanced solid features. The mixing devices, a sliding surface mixing device (SSMD) and a rotor-stator mixer (RSM), were operated continuously. Micromixing was characterized by using a competitive parallel reaction system (iodide-iodate). It was possible to achieve micromixing time from 1 to 200 ms according to the type of mixer and the operating conditions. The micromixing times assessed experimentally are in correct agreement with the theoretical ones. For boehmite precursor, the micromixing time had not a decisive influence on the crystallite size. Better control of the particle surface area was obtained considering the shear rate level, maybe due to a disordered aggregation. Conversely, reduction of the crystallite size with a decrease of the micromixing time was observed with NH4-dawsonite. A possible explanation lies in a higher local supersaturation, leading to a more intense primary nucleation. Moreover, it was possible to adjust the pore volume of the NH4-dawsonite’s aggregates with the operating conditions to quite a large extent (0.2 up to 0.8 cm3 g–1).

      PubDate: 2017-10-18T09:45:08Z
       
  • Continuous enzymatic synthesis of polycaprolactone in packed bed reactor
           using pressurized fluids
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Josamaique G. Veneral, Débora de Oliveira, Sandra R.S. Ferreira, J. Vladimir Oliveira
      Continuous processing of reagents allows high reaction yields and better operational process control, allied with cost reduction compared to batch mode. In this work, a packed-bed reactor (PBR) system using Novozym 435 for enzymatic ring-opening polymerization (e-ROP) of ɛ-caprolactone (ɛ-CL) with dichloromethane asa cosolvent in supercritical CO2 (scCO2) or in n-butane media, was investigated. The reactions carried out in scCO2 reached yields above 93wt%, average molecular weight (Mn ) of up to 31.2kDa and polydispersity (Đ) from 1.4 to 1.6 for only 15min processing. The apparent monomer conversion rate constant (kapp ) ranged from 0.094 to 0.180min−1. Otherwise, reactions performed with n-butane provided yields above 80wt%, Mn values of 25.4kDa and Đ in the range of 1.4–1.6, also obtained for 15min of reaction. The maintenance of high yields and molecular weights for up to 6 enzymatic reuses were obtained for both systems studied.
      Graphical abstract image

      PubDate: 2017-10-11T10:43:41Z
       
  • Food suspensions study with SR microtomography
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Syed F. Islam, Tomasz W. Wysokinski, George Belev, Ramana V. Sundara, Steve Whitehouse, Stefan Palzer, Michael J. Hounslow, Agba D. Salman
      The incorporation of a small amount of secondary immiscible liquid to suspensions can lead to a shift from a fluid-like structure to a paste-like structure. This is ascribed to the higher attraction of the secondary liquid to the particles, in comparison to the continuous phase. However, visual observations on the micro-scale during both long and short term time-scales, dependant on the type of secondary immiscible liquid used are yet to be reported. In the current study, the movement of various secondary immiscible liquids (water, sucrose solutions, saturated sucrose solution and glycerol) when added to a model food suspension (sucrose particles in sunflower oil) was investigated. Dynamic X-ray computed tomography was used, as a non-invasive approach, to study the mass transfer on the micro-scale and to observe the bulk movement of sucrose within the suspension. It was found that the affinity of the secondary liquid in dissolving sucrose was the primary contributor to the secondary liquid movement, with density/gravitational effects playing a minimal role.

      PubDate: 2017-10-11T10:43:41Z
       
  • A cascaded recognition method for copper rougher flotation working
           conditions
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): M. Lu, Dong H. Xie, Wei H. Gui, Liang H. Wu, Chao Y. Chen, Chun H. Yang
      Due to the complex process of copper flotation and the frequently diversified conditions of ore sources, it is difficult to identify rougher flotation conditions and maintain the stability of production process. By deeply analyzing the characteristics of the copper flotation process, the recognition system for working conditions in copper rougher is established and the cascaded recognition method is presented. At the first stage, the recognition model is built to identify feeding ore types based on fusion information of froth image local colour features and process parameters. At the second stage, the asymmetry binary tree SVM multi-class classification method with working condition priority rating (WCP-BTSVM) is used to recognize copper rougher flotation conditions. As demonstrated in the industrial experiment, the proposed method can relatively accurate identify the working conditions in copper rougher and thus can provide a solid foundation for decision-making in follow-up process control.
      Graphical abstract image

      PubDate: 2017-10-11T10:43:41Z
       
  • A bonded sphero-cylinder model for the discrete element simulation of
           elasto-plastic fibers
    • Abstract: Publication date: 16 January 2018
      Source:Chemical Engineering Science, Volume 175
      Author(s): Yu Guo, Carl Wassgren, Jennifer S. Curtis, Dandan Xu
      Based on the Discrete Element Method (DEM), a bonded sphero-cylinder model is developed to simulate flexible fibers that can undergo plastic bending deformation. In the model, a fiber is formed by connecting a number of identical sphero-cylinders using virtual bonds, which can experience bending, axial extension/compression, and twisting deformations. The elastic deformation and vibration of a single fiber are simulated and validated against elastic beam theories. In addition, an elasto-plastic constitutive model is implemented to simulate the elasto-plastic bending deformation of a fiber. The DEM results compare well with Finite Element Method (FEM) simulations, verifying the proposed elasto-plastic fiber model. By using bonded sphero-cylinders as opposed to more traditional bonded spheres, large aspect ratio fibers with smooth surfaces can be simulated effectively with fewer elements. The new constitutive model allows for the simulation of elasto-plastic materials, such as metals, plastics, and biomass.
      Graphical abstract image

      PubDate: 2017-10-04T01:52:30Z
       
 
 
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